There has been known an electronic thermometer of a type in which a probe is kept in an underarm or a hypoglottis for measuring a temperature (i.e., body temperature). For accurately measuring or predicting the temperature (i.e., body temperature), it is necessary in this type of thermometer to keep firmly a temperature measuring unit at the end of the probe in contact with a measurement target portion such as a central portion of a concavity of an underarm or a base end of a lower side of a tongue.
For example, a patent document 1 has disclosed an electronic thermometer that senses a contact state of a probe, using a switch, contact resistance, humidity, pressure (contact point), temperature comparison, change in temperature or the like. A patent document 2 has disclosed an electronic thermometer that has a pair of contact points at a surface of a thermometer body, and issues an alarm when there is no continuity between the contacts.
However, conventional sensing may cause a sensing error when an object other than a human body or an object such as a hand or a finger comes into contact with the probe. Also, even when the probe is kept in the underarm or hypoglottis, the temperature measuring unit at the end of the probe may shift from the measurement target portion or may not be firmly in contact with it, a position or direction of the probe or a closing state of the underarm is not correct. In the prior art, it is difficult to sense such a contact failure, resulting in a problem that the accuracy (prediction accuracy) of the body temperature measurement lowers or an error occurs.    Patent Document 1: Japanese Patent National Publication No. 61-500038    Patent Document 2: Japanese Utility Model Laying-Open No. 4-138249